JPH0752935B2 - Variable speed reproduction method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is an apparatus for recording / reproducing a 1-field (1-screen) television signal by dividing it into a plurality of tracks, particularly in a mode different from the recording state. The present invention relates to a reproducing method and device for reproducing a signal.

[Conventional technology]

As a device for recording and reproducing television video signals,
For example, there is a video tape recorder (hereinafter referred to as VTR).

In the conventional analog VTR, the third
As shown in the figure, a 1-field television video signal is recorded on 1 track (hereinafter referred to as a segment) (for example, described in JP-A-55-150682).

In the reproduction of the VTR as described above, there is a variable reproduction for reproducing at a speed different from the recording speed, in addition to a so-called normal mode reproduction for reproducing at the same speed as the recording speed.

In the case of reproduction in the normal mode, the head locus becomes A → B → C as shown in FIG. 3, and recording segments 1 → 2 → 3.
And then in order of 4 → 5 → 6.

However, in the case of high speed mode reproduction, which is a type of variable speed reproduction, the head locus becomes, for example, X → Y in FIG. Only play.

Therefore, as shown in FIG. 4, a noise bar is generated in the horizontal direction of the screen.

This noise bar is very unsightly if it is not fixed on the screen, so in analog VTRs, in order to fix the above noise bar on the playback screen, the rotation speed of the cylinder equipped with the playback head and the control signal are synchronized. The tape feed speed is controlled like this.

The control signal is a signal indicating the track position, and is recorded as one pulse each time the cylinder makes one revolution, for example, on a control track provided in the longitudinal direction of the magnetic tape.

Further, in order to remove the above noise bar, it is necessary to use a movable head or the like using a piezoelectric element.

[Problems to be solved by the invention]

Recently, a digital VTR for converting a television signal into a digital signal and recording / reproducing has been developed.

This device has an advantage that an image without noise bars can be reproduced by using the frame memory.

However, this device must record high-speed and large-capacity data as compared with an analog VTR, so it is very difficult to record one field of information in one segment at the current recording density. Therefore, a method of dividing the data of one field into a plurality of segments and recording the data is adopted.

When the data of one field is divided into a plurality of segments as described above, when reproduced at a speed different from that at the time of recording, the following problems occur.

For example, as shown in FIG. 5, the image of one field is divided into three segments D, E, and F, and the information of D is segment 1 in FIG. 3, the information of E is segment 2, and the information of F is When recorded in segment 3, for example, when reproducing in a high speed mode of 3 times, the head locus becomes X → Y in FIG. 3, and the reproduced portion is the front part of segment 1, the central part of segment 2, and segment 3 The rear part, the front part of the segment 4, the central part of the segment 5, and the rear part of the segment 6.

However, the segments 1 and 4, 2 and 5, 3 and 6 in FIG.
Are images different from each other by one field, that is, since they are at the same image position, the reproduced signal is only a part on the screen.

Therefore, as shown in FIG. 6, there is a problem that only a part of the entire screen can be reproduced.

In addition, a method for shuffling data (for example, Japanese Patent Laid-Open No.
No. 164408), only the image data at the same screen (pixel) position can be captured at the above-mentioned reproduction speed, so that there is a problem that the reproduced image quality deteriorates.

It is an object of the present invention to provide a reproducing method and apparatus capable of obtaining a good image even in variable speed reproduction when a 1-field television video signal is divided into several tracks and recorded.

[Means for solving problems]

The purpose of the above is to control the tape feed speed and to control the cylinder rotation phase and the control signal (CTL) to reproduce from the tape.
Can be achieved by desynchronizing.

That is, by asynchronously performing the above-described process, the entire screen is constructed in a short cycle and good variable speed reproduction is performed.

[Action]

First, the recording track on the tape and the locus of the reproducing head will be described in detail.

"Track pattern coordinate method" (Yokohori, Okamoto, Igarashi "One analysis method of VTR track pattern", Television Society of Japan, 1980) as one of the methods to visualize the track locus in variable speed playback mode and simplify the analysis. Annual national competition,
7-17).

The track pattern coordinate method described above treats the running tape as a stationary coordinate system by arranging the recording track patterns in a plane and repeatedly arranging them, and the movement of the tape and the head is treated as one locus. It is a method of forming and obtaining a continuous track pattern in consideration of the head width.

This track pattern expresses the track of the video head under various conditions. The track of the read head is drawn on this track, and the equation is plotted on this drawing to solve it. You can easily ask for it.

Hereinafter, the ratio of the reproducible screen in the variable reproduction is calculated by the above method.

For example, as shown in FIG. 5, it is assumed that the television screen is divided into three segments and a guard band is provided for recording.

At this time, if the recording segments 1 to 6 in FIG. 3 are expressed by the track pattern coordinate method, they become 1 to 6 in FIG.

The horizontal axis of FIG. 7 represents time, and the vertical axis represents the difference between the tape movement amount during normal reproduction and the tape movement amount during reproduction in each mode.

This figure also shows the relationship between the track pitch T _P , the track width T _W , and the head width H _W. Further, Q and R in the figure show a locus Q at the lower end of the head and a locus R at the upper end of the head when the tape feed speed is 2.5 times that in normal reproduction.

Further, S represents the time for the cylinder drum to make a half rotation, that is, the time for one track. For example, when a screen of one field of an NTSC television signal is divided into three segments and recorded, it is about 5.55 ms. Is.

When the screen of one field is divided into three segments, 1 and 4, 2, 5, and 3 and 6 in FIG. 7 are at the same position on the screen.

Therefore, the locus Q of the lower end of the head shown in FIG.
Can be expressed by being superimposed on the first block of FIG. 8, that is, the first field screen.

A line segment a of the locus Q at the lower end of the head in FIG. 8 is folded into a ', and similarly b is b', c is c ', d is d', e
Is folded into e'and f into f '.

Here, when 70% or more of the maximum envelope is reproducible, when the reproducible portion is represented on the track pattern, the hatched portion in FIG. 9 is obtained. In this case, a ′ to f ′ are loci at the lower end of the head, and a ″ to f ″ are loci at the upper end of the head.

When the reproducible portion when the reproduction speed is 2.5 times the normal speed is represented by the configuration of the television screen, 80 to 90% can be reproduced on the entire screen as shown in FIG.

On the other hand, in the above-described 3 × speed reproduction, only about 10 to 20% of the entire screen can be reproduced.

When the one-field television screen is composed of a plurality of segments as described above, the reproducible portion and its area differ depending on the reproduction speed.

FIGS. 11 (A) and 11 (B) are diagrams showing the screen realization rate (reproducible screen area / total screen area and 100%) when the reproduction time is limited to 2 fields (33.3 msec). .

The values in Fig. 11 are the number of segments and the track pitch.
T _P is 40 μm, track width T _W is 20 μm, head width H _W is 25 μm
It is a value for the case of m.

As can be seen from FIG. 11, the reproduction speed is an integral multiple of the recording speed,
When it is a multiple of 3 or a multiple of 1.5, the screen representation rate deteriorates significantly.

That is, when the playback speed is set to a multiple of (the number of segments recording 1 field / 1), a multiple of (the number of segments recording 1 field / 2), and a multiple of (the number of segments recording 1 field / 3) The realization rate becomes significantly worse.

Here, the tape feed speed V at the time of variable speed reproduction is set to the following (1)
Expressed as a formula.

V = V ₀ × Tr × N / M (1) where V ₀ is the tape feed speed during recording, Tr is the number of segments in one field, N is an integer other than 0, and M is an integer of 1 or more. , V = V ₀ is excluded.

Then, G = M × G ₁ (2) is approximately established between the screen realization rate G when the reproduction time is not limited and the integer M.

However, G ₁ is the screen realization rate in the state (M = 1, N = 1) shown in FIG. 5, and the tape feed speed V at that time
= V ₀ × Tr.

As can be seen from equation (2) above, the screen realization rate G is 100%.
The condition which does not satisfy is when M is less than 1 / G ₁ . For example, the number of segments in one field is 3, and M = 1, N = 1
When the screen realization rate G _{1 at the} tape feeding speed (V = V ₀ × Tr) in 20 is 20%, M in the equation (1) is an integer of 1 or more and less than 5. And a multiple of (3/1), (3 /
If the tape feed speed is a multiple of 2), a multiple of (3/3), or a multiple of (3/4), the screen realization rate becomes poor.

In order to improve the screen realization rate, the control signal (CTL) indicating the cylinder rotation phase and the track position may be made asynchronous at the tape feeding speed at which the screen realization rate becomes poor as described above.

In a normal reproducing operation, the rotation of the cylinder is controlled so as to be in phase synchronization with the control signal (CTL signal) reproduced from the magnetic tape. The running speed of the magnetic tape is controlled so that the phase relationship between the CTL signal and the synchronizing signal of the television signal input to the magnetic recording / reproducing apparatus is synchronized. Therefore, making asynchronous means stopping some or all of these synchronous controls.

With such non-synchronization, the phase relationship between the rotation of the cylinder and the running of the magnetic tape cannot be maintained accurately. That is, the rotational speed of the cylinder and the running speed of the magnetic tape are
Basically, the control signal from the system control circuit 1 is controlled so that the correspondence relationship is maintained,
By canceling the above-mentioned synchronous control, in other words, by desynchronizing the rotation phase of the cylinder and the control signal such as the CTL signal reproduced from the magnetic tape, a phase shift occurs.

For example, at a tape speed of 3 ×, a regular fixed 3 × speed is not always realized, but a slow phase shift occurs. That is, the instantaneous speed fluctuates slightly such as 3.01 times or 2.99 times, and is 3 on average.
It means double speed.

At the non-synchronized triple speed, a phase difference is generated between the cylinder rotation phase and the track position depending on the tape speed.
The phase difference becomes the difference between the reproduction positions on the screen. For example, at the triple speed, the rotation phase of the cylinder and the track phase of the magnetic tape change by 360 degrees per second means that all positions on one screen are scanned per second.

In the case of 2.5 times speed with phase synchronization, almost all the screen is scanned by 8 rotations, so the time for full screen scanning is 5.5 msec x 8 = 4
It will be 4 msec. On the other hand, in the case of asynchronous, there is a problem that the time is 1 second as described above, the time required for full-screen scanning is long, and it is not always constant. However, at the 3 × speed in which the phase is synchronized, only about 20% (see FIG. 11) is updated, so the image quality improvement in the non-synchronized case is obvious compared to this case.

Even if the asynchronous method is applied at a tape feeding speed having a good screen realization rate, the realization rate is only further improved and no problem is naturally caused.

〔Example〕

FIG. 1 is an embodiment of the present invention and shows a basic block diagram of a VTR cylinder and capstan servo system.

The apparatus shown in FIG. 1 is roughly divided into a system control circuit 1 for generating control signals in various modes such as reproduction, recording, fast forward, and slow, a cylinder control circuit 2 for controlling the circuit speed phase of a cylinder, and a tape feed speed. It comprises a capstan control circuit 4 for controlling the phase.

The system control circuit 1 is for playing, recording, fast-forwarding,
Control signals 7 and 10 are generated by a mode signal representing each mode such as slow and the like to control the cylinder control circuit 2 and the capstan control circuit 4 in each mode.

The cylinder control circuit 2 determines each mode by the control signal 7 and compares the DTP signal 9 representing the rotation of the cylinder with the VD signal 16 provided from the video signal or the oscillator to generate the cylinder motor control voltage 8. The rotation speed and phase of the cylinder motor 3 are controlled accordingly.

The capstan control circuit 4 discriminates the mode by the control signal 10, detects the speed by the CFG signal 12 representing the rotation of the capstan, and controls the rotational speed of the capstan mode 5 in each mode.

At the same time, the capstan control circuit 4 controls the tape feed speed and phase.
The CTL signal 13 (control signal) is generated from the VD signal 16, and this is recorded on the magnetic tape 15 by the CTL head 14.

In the reproduction mode, the CTL signal 13 read by the CTL head 14 is compared with the reference signal to generate the capstan motor control voltage 11, which controls the rotation speed and phase of the capstan motor 5.

Next, FIG. 2 shows a detailed block diagram of the capstan control circuit 4 in the present invention.

The circuit shown in FIG. 2 includes a reference signal generation circuit 20 and a phase control circuit 2
1, a frequency divider 22, a frequency generator 23, an adder 27 and a switch 28.

Hereinafter, the control of the tape feeding speed during reproduction will be described in detail.

The system control circuit 1 generates the control signal 10 in each mode and controls the phase control circuit 21 and the frequency dividing circuit 22.

The phase control circuit 21 generates the phase error voltage 25 by comparing the reference signal 24 generated by the reference signal generation circuit 20 with the CTL signal 13 or the reference signal 24.

The CTL signal 13 and the reference signal 24 are switched by the switch 28 according to each mode.

The frequency divider circuit 22 varies the frequency division ratio according to the control signal 10 and variably divides the CFG signal 12 according to each mode.

Further, the frequency-divided signal is converted into a voltage by the frequency generator 23 to generate a speed error voltage 26.

Then, the phase error voltage 25 and the speed error voltage 26 are added by the adder 27.
Is added and is given to the capstan mode 5 as the capstan motor control voltage 11 to control the tape feed speed and phase in each mode.

As described above, the tape feeding speed V during variable speed reproduction is a multiple of (the number of segments recording 1 field / 1), the multiple of (the number of segments recording 1 field / 2) of the tape feeding speed during recording, ( When it is a multiple of the number of segments for recording one field / 3), the screen reality ratio deteriorates, and some portions cannot be reproduced.

Therefore, during variable speed reproduction, that is, when the recording speed and the reproduction speed are different, the switch 28 is switched to the contact 30 side. As a result, the CTL signal 13 from the CTL head 14 is no longer input, so that the tape feeding speed is controlled to be a predetermined speed corresponding to the reference signal supplied from the reference signal generation circuit 20, regardless of the CTL signal 13. It Like this CTL
By making the signal independent of the tape feed speed, that is, by making the phase relationship between the position of the recording track and the magnetic tape speed asynchronous, the positional relationship between the rotation of the cylinder and the recording track becomes asynchronous, and all of the one screen is displayed. You will be scanning the location and can play the full screen.

Further, even if the speed is other than the above speed, a phase difference may be caused in the tape feeding.

According to the present embodiment, good variable speed reproduction can be performed by switching the switch 28 according to each mode and tape feeding speed.

Further, since the circuit is simple, it is easy to realize, the circuit scale is small, and it is economically advantageous.

〔The invention's effect〕

According to the present invention, it is possible to obtain a good variable-speed reproduced image even at a reproducing speed at which a part not reproduced on the television screen occurs.

In addition, a good variable speed reproduction image can be obtained by avoiding the reproduction speed as described above.

It goes without saying that the present invention can be applied to the component system and the data shuffling system.

Further, according to the present invention, it is possible to achieve good variable speed reproduction with good image quality by a simple circuit and method, and it is economically advantageous because the circuit is simple.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing a servo system of a capstan in an embodiment of the present invention, and FIG. 3 is a diagram showing tracks on a magnetic tape. FIG. 4 is a diagram showing a normal mode and a high-speed mode in the case of reading, FIG. 4 is a diagram showing a television reproduction screen when one field signal is recorded in one segment, and FIG. 5 is a division of a segment of the one field screen. Fig. 6 is a diagram showing a television reproduction screen, Fig. 7 is a diagram showing a head locus and a track, and Fig. 8 is a diagram showing a head locus and a track superimposed on the first block.
FIG. 9 is a diagram showing a reproducible portion, FIG. 10 is a diagram showing a television reproduction screen, and FIGS. 11 (A) and 11 (B) are diagrams showing the relationship between the reproduction speed and the screen realization rate. <Description of symbols> 1 ... System control circuit 2 ... Cylinder control circuit, 3 ... Cylinder motor 4 ... Capstan control circuit 5 ... Capstan motor 6 ... Mode signal 7, 10 ... Control signal, 8 ...... Cylinder motor control voltage 9 ...... DTP signal 11 ...... Capstan motor control voltage 12 ...... CFG signal, 13 ...... CTL signal 14 ...... CTL head, 15 ...... Magnetic tape 20 ...... Reference signal generation circuit, 21 ...... Phase control circuit 22 …… Dividing circuit 23 …… Frequency generator 24 …… Reference signal 25 …… Phase error voltage 26 …… Speed error voltage 27 …… Adder 28 …… Switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiichi Mita 1-280 Higashi Koigakubo, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inventor Shinzo Doi 1-280 Higashi Koigakubo, Kokubunji, Tokyo Hitachi Ltd. (72) Inventor Akira Saito 1410 Inada, Katsuta, Ibaraki, Inada, Hitachi Ltd.Tokai Plant (72) Inventor Tetsuya Amano, 292, Yoshida, Totsuka-ku, Yokohama, Kanagawa Hitachi Video Engineering Co., Ltd.

Claims (2)

[Claims] 1. A 1-field signal of a television signal is divided into two or more blocks, and each block is recorded and reproduced by a rotary head mounted on a cylinder as a track inclined at a constant angle with respect to the longitudinal direction of a magnetic tape. In a magnetic recording / reproducing apparatus for recording / reproducing a control signal in the longitudinal direction of the magnetic tape in order to synchronize the rotational phase of the cylinder during reproduction with the magnetic tape, a predetermined speed different from that during recording during reproduction. When the magnetic tape is run by and the cylinder is rotated at a predetermined speed corresponding thereto, the porcelain tape is moved at the predetermined speed irrespective of the control signal reproduced from the magnetic tape. By controlling it to run, the rotation phase of the cylinder and the porcelain tape are reproduced. A variable speed reproduction method characterized in that the phase of the control signal is asynchronous. 2. A signal of one field of a television signal is divided into two or more blocks, and each block is recorded / reproduced by a rotary head mounted on a cylinder as a track inclined by a certain angle with respect to the longitudinal direction of the magnetic tape. In the magnetic recording / reproducing apparatus for recording / reproducing a control signal in the longitudinal direction of the magnetic tape in order to synchronize the rotational phase of the cylinder with the magnetic tape during reproduction, the control signal is reproduced from the porcelain tape. When the traveling speed of the porcelain tape during reproduction is the same as that during recording, the traveling speed of the magnetic tape is synchronized with the rotation phase of the cylinder and the phase of the control signal reproduced by the first means. When a magnetic tape running speed during playback is a predetermined speed different from that during recording, Regardless of the control signal reproduced from the magnetic tape,
Second means for generating a signal for controlling the running speed of the magnetic tape so as to run the magnetic tape at the predetermined speed set in advance, and controlling the running speed of the magnetic tape according to the signal. Variable playback device.